Set of Real Numbers Symbol
The set of real numbers symbol is the Latin capital letter “R” presented with a double struck typeface. The symbol is typically used to express that a variable is a member of the set of real numbers:
In plain language, the exppresion above means that the variable is a member of the set of real numbers.
The set of real numbers contains the set of rational numbers as well as irrational numbers like pi, e, and the square root of two.